The present invention relates to a wave transmitter/receiver and wave reflector which can be mounted directly to the interior surface of the skin of the aircraft, and does not depend upon the use of vibrating plates or other separate sensors that require modification of the aircraft surface.
The use of ultrasonic contaminant detectors is described in U.S. Pat. No. 5,629,485, where the orientation of transmitter and receivers onto a plate or sheet is taught, and a guided wave is transmitted through the sheet. The receiver receives a signal from the sheet and the presence of a contaminant on the sheet, such as ice, can be determined by the characteristics received of the wave or signal.
Additionally, U.S. Pat. No. 5,922,958 discloses a contaminant detection device that includes a plate that can be mounted onto the skin of an aircraft, and which includes a reflecting groove formed in the plate at a location spaced from a transducer/receiver.
U.S. Pat. No. 5,729,508 discloses an environmental seal for an acoustic transducer that can be used for transmitting ultrasonic vibrations in ice detecting systems such as the present invention.
U.S. Pat. No. 4,461,178 also discusses contaminant detection using guided waves.
The present invention relates to an ultrasonic ice detection system which can be mounted directly onto interior surfaces of an aircraft skin or outer wall, or on a component of an airborne vehicle, such as the inlet of a turbine engine, or on other structures, without having a separate sheet or plate installed. The sensor is non-intrusive in the form disclosed. The invention uses a transmitter/receiver oriented to transmit vibrations at a particular phase velocity. The vibration will propagate through the aircraft skin or wall, and a reflector bar is located at a predetermined position to provide an adequate reflected wave. The reflector location is selected to optimize performance.
Both the transducer assembly and the reflector bar are secured to the interior surface of the skin of an aircraft, so that the sensor components mount interiorly of the aircraft. There is no need for providing a separate waveguide plate that requires alteration of the aircraft structure or the aircraft skin. There is also no need to cut reflective surfaces on the aircraft or engine housing wall itself. Providing an acoustic energy path along the skin or wall that is free of rivets or other attached structures insures propagation and the ability to detect changes in vibrational frequency and/or amplitude due to contaminants, such as ice, bonding to exterior surfaces of the aircraft skin.
In one aspect of the invention, as shown, the moveable slat at the leading edge of the wing, which is used for changing lift characteristics of the wing, is illustrated as an exemplary form of the invention. The exemplary form shows that the acoustic energy can be transmitted along curved wall structures to the reflector bar, and as well as being capable of reflecting acoustic energy along flat plates.
Parameters for determining the height and depth of the reflector can be optimized by experimental procedures, or by finite element analysis or boundary element analysis utilizing numerical methods.